In print processing based on image data by using a digital copier, a printer or the like, in some cases, it is desired that a preview of image to be printed is displayed on a monitor screen to check whether or not the result of printing that was intended can be obtained. FIG. 12 is a block diagram showing the construction of image display apparatus having a function of presenting a preview of image data prior to printing.
In the conventional display apparatus in FIG. 12, an image read from a hard disk (HD) 102 or a scanner 103 is inputted into a controller 110 via an HD I/F 107 or scanner I/F 108 of a printer interface (I/F) board 101. For the sake of conservation of memory capacity, the input image is compressed by an image compression unit 114 included in the controller 110 and stored into an image memory 113.
Further, when the image data inputted into the image memory 113 is print-outputted, the data is expanded by an image expansion unit 115 included in the controller 110, outputted to a printer 104 via a printer I/F 109, and print-outputted.
On the other hand, in a case where the image data is previewed prior to printing, the image data is expanded by the image expansion unit 115 included in the controller 110, and outputted to a monitor screen 105 via a monitor I/F 112. Note that instructions for the above-described printing and preview are made by a user from an operation unit 106, and various instruction information are sent to the controller 110 via an operation I/F 111.
In a case where a preview image is displayed on a monitor screen 105, in some cases, it is desired that not only the entire image but also to an enlarged image part is displayed so as to check details of the image to be printed. Further, to check an enlarged image part, it is desired to check the image in a wide range while scrolling the image displayed on the monitor screen 105.
To satisfy such requirements, it is necessary to provide the image display apparatus having the above construction with means for enlargement and reduction of image and means for scrolling an image display area and in this case, the production cost of the apparatus as a product increases. Accordingly, the above-described image preview function may be installed in the image display apparatus as another board or LSI, and the controller is arranged such that the function can be added in correspondence with product specification.
FIG. 13 is a block diagram showing the construction of the image display apparatus shown in FIG. 12, to which means for realizing a preview function including an image enlargement/reduction function and scroll function is connected as another board. In the image display apparatus shown in FIG. 13, an image stored in an image memory 132 is displayed as a preview image on a monitor screen 136 based on an instruction from an operation input unit 126. In this case, first, the entire image is expanded by an image expansion unit 134 included in a controller 130 and temporarily stored in the image memory 132. Then only an image part necessary for display on the monitor screen 136 is transferred to a local image memory 139 connected to a preview board 121.
Next, the image data is converted by an image enlargement/reduction unit 137 on the preview board 121 into image data at a scale designated from the operation input unit 126. Further, the data is converted by a color space converter 138 into data having color components and image data format appropriate to screen display. The converted image data is stored into an image buffer in the local image memory 139. Then, a monitor I/F 135 sequentially reads the image data from an image display area within the image buffer and outputs the data to a monitor screen 136.
Further, in a case where an instruction to scroll the image displayed on the monitor screen 136 is inputted from the operation input unit 126, similarly, newly-required image data within a range necessary for display is sequentially transferred to the local image memory 139 connected to the preview board 121. Thereafter, the image data is converted by the image enlargement/reduction unit to image data at a designated scaling designated 137, and converted by the color space converter 138 to data having color components and image data format appropriate to image display. Then, the converted image data is stored into the image buffer area in the local image memory 139 thereby image scroll is realized. Note that if the image buffer area is used as a ring buffer, a newly stored image is written over an image area which disappears from the display screen by scroll.
Further, in the image display apparatus as shown in FIG. 13, it may be arranged such that the local image memory 139 has a sufficiently large size and the entire enlarged image data can be stored in addition to image data in a necessary range. In this image display apparatus, to display a preview image in accordance with an instruction from the operation input unit 126, first, the entire image is expanded by the image expansion unit 134 included in the controller 130, then transferred to the local image memory 139 connected to the preview board 121. Next, the image data is converted by the image enlargement/reduction unit 137 to an image at a designated scaling, and converted by the color space converter 138 to image data having color components and image data format appropriate to screen display. Then the converted image data is stored into the image buffer area connected to the local image memory 139.
The monitor I/F 135 sequentially reads the image data from the image display area in the image buffer area and outputs the data to the monitor screen. Further, if an instruction for screen scroll is inputted from the operation unit 126, the image display area is sequentially changed by using display area scroll means provided in the monitor I/F 135, thereby the image displayed on the monitor screen 136 is scrolled.
However, in the example of FIG. 13, in the former case of image display apparatus where necessary image data is sequentially transferred to the local image memory 139, as it takes time from the instruction for image scroll before the image display, image scroll cannot be smoothly performed. Further, in the case of image display apparatus where the entire image data is stored in the local image memory 139, although smooth scroll is realized, a memory capacity for storing enlarged image data is necessary, accordingly, the product cost increases.
Further, in any of the arrangements, it is necessary to previously expand the entire image. It takes time to perform the expansion processing, and further, as the expanded image data is non-compressed data, much time is required for transfer of the image data from the image memory to the local image memory.